Method for operating an internal combustion engine

ABSTRACT

An internal combustion engine ( 1 ), especially of a motor vehicle, is described. The engine ( 1 ) is provided with a combustion chamber ( 4 ) into which fuel can be injected in a first operating mode during a compression phase and in a second operating mode during an induction phase. The engine ( 1 ) is provided with a control apparatus ( 18 ) for switching over between the operating modes. The engine ( 1 ) includes an exhaust-gas recirculation having an exhaust-gas recirculation valve ( 14 ). The engine ( 1 ) is switched by the control apparatus ( 18 ) into the first operating mode when the exhaust-gas recirculation valve ( 14 ) is jammed in the open state.

FIELD OF THE INVENTION

The invention relates to a method for operating an internal combustionengine, especially of a motor vehicle, wherein fuel is injected into acombustion chamber in a first operating mode during a compression phaseand in a second operating mode during an induction phase. In the method,there is a switchover between the operating modes and the internalcombustion engine has an exhaust-gas recirculation with an exhaust-gasrecirculation valve. The invention likewise relates to a correspondinginternal combustion engine as well as a corresponding control apparatusfor an engine of this kind.

BACKGROUND OF THE INVENTION

A method of this kind, an internal combustion engine of this kind and acontrol apparatus of this kind are all, for example, known from aso-called gasoline direct injection. There, fuel is injected into thecombustion chamber of the engine in a homogeneous operation during theinduction phase or in a stratified operation during the compressionphase. The homogeneous operation is preferably provided for thefull-load operation of the engine; whereas, the stratified operation issuitable for idle operation and part-load operation.

In an internal combustion engine of this kind, fault functions canoccur. Accordingly, it is, for example, possible that the exhaust-gasrecirculation valve jams or can no longer be moved. In this case, itmust be ensured that the engine does not go into a critical operatingstate.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method for operating theinternal combustion engine wherein it is ensured that fault functions ofthe exhaust-gas recirculation do not lead to critical operating statesof the engine.

This object is solved in accordance with the invention in a method ofthe kind mentioned initially herein in that the engine is switched overinto the first operating mode when the exhaust-gas recirculation valvejams in the open position. The task of the invention is solvedcorrespondingly in an internal combustion engine and a control apparatusof the kind mentioned initially herein.

If the exhaust-gas recirculation valve jams in the open position, thenthe engine is switched over into the stratified operation in accordancewith the invention. In the stratified operation, the open exhaust-gasrecirculation valve can be easily considered in the control (open loopand/or closed loop) of the engine. A critical state can therefore notoccur. With the selection of the stratified operation as an emergencyoperation, a reliable operation of the engine is ensured. Thedisadvantage that, in stratified operation, only a reduced torque can begenerated by the engine is greatly outweighed by the advantage of areliable operation.

In an advantageous further embodiment of the invention, the engine isswitched over into the second operating mode when the exhaust-gasrecirculation valve is jammed in the closed state.

If the exhaust-gas recirculation valve jams in the closed state, thenthe engine is switched over into the homogeneous operation in accordancewith the invention. In the homogeneous operation, and for a closedexhaust-gas recirculation valve, the engine can be easily operated andespecially without exceeding exhaust-gas limit values. A reliableoperation of the engine is thereby provided also in this fault case.

In a further advantageous embodiment of the invention, the exhaust-gasrecirculation valve is closed in another fault function of theexhaust-gas recirculation and the engine is switched over into thesecond operating mode. It is especially advantageous when a jamming ofthe exhaust-gas recirculation valve is determined with the aid of asensor.

Of special significance is the realization of the method of theinvention in the form of a control element which is provided for acontrol apparatus of an engine, especially of a motor vehicle. A programis stored on the control element which is capable of being run on acomputer, especially on a microprocessor, and is suitable for executingthe method according to the invention. In this case, the invention isrealized by a program stored on the control element so that this controlelement, which is provided with the program, defines the invention inthe same way as the method which the program can carry out. Especiallyan electric storage medium can be used as a control element, forexample, a read-only-memory or a flash memory.

Further features, application possibilities and advantages of theinvention will become apparent from the following description ofembodiments of the invention which are illustrated in the drawing. Alldescribed or illustrated features define the subject matter of theinvention by themselves or in any desired combination independently oftheir summary in the patent claims or their dependency as well asindependently of their formulation or presentation in the descriptionand/or in the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The single FIGURE of the drawing shows a schematic block circuit diagramof an embodiment of an internal combustion engine according to theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

In the FIG., an internal combustion engine 1 of a motor vehicle is shownwherein a piston 2 is movable back and forth in a cylinder 3. Thecylinder 3 is provided with a combustion chamber 4 which is, inter alia,delimited by the piston 2, an inlet valve 5 and an outlet valve 6. Anintake manifold 7 is coupled to the inlet valve 5 and an exhaust-gaspipe 8 is coupled to the outlet valve 6.

An injection valve 9 and a spark plug 10 project into the combustionchamber 4 in the region of the inlet valve 5 and of the outlet valve 6.Fuel can be injected into the combustion chamber 4 via the injectionvalve 9. The fuel in the combustion chamber 4 can be ignited with thespark plug 10.

A rotatable throttle flap 11 is mounted in the intake manifold 7 and aircan be supplied via the throttle flap to the intake manifold 7. Thequantity of the supplied air is dependent upon the angular position ofthe throttle flap 11. A catalytic converter 12 is accommodated in theexhaust-gas pipe 8 and this catalytic converter serves to purify theexhaust gases arising because of the combustion of the fuel.

An exhaust-gas recirculation pipe 13 leads from the exhaust-gas pipe 8back to the intake manifold 7. An exhaust-gas recirculation valve 14 isaccommodated in the exhaust-gas recirculation pipe 13. With this valve14, the quantity of the exhaust gas, which is recirculated into theintake manifold 7, can be adjusted. The exhaust-gas recirculation pipe13 and the exhaust-gas recirculation valve 14 define a so-calledexhaust-gas recirculation.

A tank-venting line 16 leads from a fuel tank 15 to the intake manifold7. A tank-venting valve 17 is mounted in the tank-venting line 16 and,with this valve 17, the quantity of the fuel vapor from the fuel tank15, which is supplied to the intake manifold 7, can be adjusted. Thetank-venting line 16 and the tank-venting valve 17 define a so-calledtank venting.

The piston 2 is displaced by the combustion of the fuel in thecombustion chamber 4 into a back and forth movement which is transmittedto a crankshaft (not shown) and applies a torque thereto.

Input signals 19 are applied to a control apparatus 18 and these signalsdefine measured operating variables of the engine 1. For example, thecontrol apparatus 18 is connected to an air-mass sensor, a lambdasensor, an rpm sensor and the like. Furthermore, the control apparatus18 is connected to an accelerator pedal sensor which generates a signalwhich indicates the position of an accelerator pedal, which can beactuated by the driver, and therefore indicates the requested torque.The control apparatus 18 generates output signals 20 with which theperformance of the engine 1 can be influenced via actuators orpositioning devices. For example, the control apparatus 18 is connectedto the injection valve 9, the spark plug 10 and the throttle flap 11 andthe like and generates the signals required to drive the same.

The control apparatus 18 is, inter alia, provided to control (open loopand/or closed loop) the operating variables of the engine 1. Forexample, the fuel mass, which is injected by the injection valve 9 intothe combustion chamber 4, is controlled (open loop and/or closed loop)by the control apparatus 18 especially with respect to a low fuelconsumption and/or a low development of toxic substances. For thispurpose, the control apparatus 18 is provided with a microprocessor inwhich a program is stored in a memory medium, especially in a flashmemory, and this program is suited to execute the above-mentionedcontrol (open loop and/or closed loop).

The engine 1 of FIG. 1 can be operated in a plurality of operatingmodes. Accordingly, it is possible to operate the engine 1 in ahomogeneous mode of operation, a stratified mode of operation, ahomogeneous lean operation and the like.

In the homogeneous operation, the fuel is injected by the injectionvalve 9 during the induction phase directly into the combustion chamber4 of the engine 1. The fuel is thereby substantially swirled up toignition so that an essentially homogeneous air/fuel mixture arises inthe combustion chamber 4. The torque to be generated is adjusted by thecontrol apparatus 18 essentially via the position of the throttle flap11. In homogeneous operation, the operating variables of the engine 1are so controlled (open loop and/or closed loop) that lambda is equal toone. The homogeneous operation is especially used at full load.

The homogeneous lean operation corresponds substantially to thehomogeneous operation, however, the lambda is set to a value of lessthan one.

In stratified operation, the fuel is injected by the injection valve 9directly into the combustion chamber 4 of the engine 1 during thecompression phase. In this way, no homogeneous mixture is present in thecombustion chamber 4 with the ignition by the spark plug 10; instead, afuel stratification is present. The throttle flap 11 can be completelyopened except for requests, for example, of the exhaust-gasrecirculation and/or of the tank venting and the engine 1 can thereby beoperated dethrottled. The torque to be generated is, in stratifiedoperation, substantially adjusted via the fuel mass. With the stratifiedoperation, the engine 1 can be operated especially at idle and at partload.

There can be a back and forth switching or switchover between theabove-mentioned operating modes of the engine 1. Such switchovers areexecuted by the control apparatus 18.

In the operation of the engine 1, faults in the exhaust-gasrecirculation can occur, which trigger different fault reactions. Here,at least three cases can be distinguished.

(1) The exhaust-gas recirculation valve 14 jams in the open state andcan therefore no longer be closed. If an exhaust-gas recirculation valve14, which jams in the open state, is determined, for example, by aposition sensor or other measures, then the engine 1 is switched intothe stratified operation. In the stratified operation, the engine 1 canbe operated with limited engine power even with an open exhaust-gasrecirculation valve 14 so that an emergency operation is possible. Theexhaust-gas limit values can be maintained.

(2) The exhaust-gas recirculation valve 14 jams in the closed state andcan no longer be opened. If an exhaust-gas recirculation valve 14 jammedin the closed state is determined, then the engine 1 is switched overinto the homogeneous operation. In the homogeneous operation, the engine1 can be easily operated with the exhaust-gas recirculation valve 14closed without exceeding exhaust-gas limit values. Basically, thestratified operation would also be possible, but here, prescribedexhaust-gas limit values, if required, could no longer be maintained.

(3) Some other fault is determined in the exhaust-gas recirculation orin the control (open loop and/or closed loop) of the exhaust-gasrecirculation and the exhaust-gas recirculation valve 14 can be closed.In this case, the engine 1 is switched over into the homogeneousoperation and the exhaust-gas recirculation valve 14 is closed. Asalready explained, the engine 1 can be easily operated in thehomogeneous operation even with a closed exhaust-gas recirculation valve14 without affecting exhaust-gas limit values.

The determination of a fault in the exhaust-gas recirculation or on theexhaust-gas recirculation valve 14 can take place directly or indirectlyby the control apparatus 18 with the aid of sensors and/or via thediagnosis of the actuator which drives the exhaust-gas recirculationvalve 14 or via some other method measures. The corresponding emergencyoperation is selected and adjusted in dependence upon the detected faultby the control apparatus 18 in correspondence to the above cases.Thereafter, an input into a fault memory of the control apparatus 18takes place.

What is claimed is:
 1. A control element including a read-only-memory orflash memory for a control apparatus of an internal combustion engineincluding an engine of a motor vehicle, the engine including anexhaust-gas recirculation system having an exhaust-gas recirculationvalve, said control element comprising a program stored on said controlelement which can be run on a computing apparatus including amicroprocessor, and said program being configured to carry out themethod steps of: injecting fuel into a combustion chamber of said enginein a first operating mode during a compression phase and in a secondoperating mode during an induction phase; and, switching said engineinto said first operating mode when said exhaust-gas recirculation valveis jammed in the open state thereof.
 2. An internal combustion engineincluding an engine of a motor vehicle, the engine comprising: acombustion chamber wherein fuel is injectable in a first operating modeduring a compression phase and in a second operating mode during aninduction phase; a control apparatus for controlling a switchoverbetween said first and second operating modes; an exhaust-gasrecirculation system having an exhaust-gas recirculation valve; and,said control apparatus including means for switching said engine intosaid first operating mode when said exhaust-gas recirculation valve isjammed in the open state thereof.
 3. A control apparatus for an internalcombustion engine including an engine of a motor vehicle, the enginehaving a combustion chamber into which fuel can be injected in a firstoperating mode during a compression phase and in a second operating modeduring an induction phase, the engine including an exhaust-gasrecirculation system having an exhaust-gas recirculation valve, thecontrol apparatus comprising: means for injecting fuel into a combustionchamber of said engine in a first operating mode during a compressionphase and in a second operating mode during an induction phase; and,means for switching said engine into said first operating mode when saidexhaust-gas recirculation valve is jammed in the open state thereof. 4.A method for operating an internal combustion engine including aninternal combustion engine of a motor vehicle, the engine including anexhaust-gas recirculation system having an exhaust-gas recirculationvalve and the method comprising the steps of: injecting fuel into acombustion chamber of said engine in a first operating mode during acompression phase and in a second operating mode during an inductionphase; and, switching said engine into said first operating mode whensaid exhaust-gas recirculation valve is jammed in the open statethereof.
 5. The method of claim 4, wherein the engine is switched intothe second operating mode when the exhaust-gas recirculation valve isjammed in the closed state.
 6. The method of claim 4, wherein, foranother fault function of the exhaust-gas recirculation system, theexhaust-gas recirculation valve is closed and the engine is switchedinto the second operating mode.
 7. The method of claim 4, wherein ajamming of the exhaust-gas recirculation valve is determined with theaid of a sensor.